Heat exchangers are widely used in industrial and other processes to either heat or cool one stream, often referred to as a process stream, using another, which may be referred to as a heating or cooling medium. The heat exchanger generally comprises one or more channels for the process stream and one or more channels for the heating or cooling medium, the channels being physically separated by walls. Heat transfer occurs through the walls from the hotter to the colder stream. The walls should therefore be made of a highly conductive material, and usually are made of metal. Stainless and other steels are commonly used.
The present invention relates to the treatment of a heat exchanger which in “operation” is used to cool a process water stream (“process water”) using a cooling medium, and in particular for cooling process water which has been in contact with polymer particles. (“Operation” as used herein means when the heat exchanger is being operated in its normal or designed manner to cool the process stream.)
It has been found that certain constituents in the process water can be deposited on the walls of the heat exchanger. These can reduce the rate of heat transfer through the walls, which can reduce the effectiveness of the heat exchanger. This process is generally referred to as “fouling”.
If the effectiveness of the heat exchanger at cooling the process water is reduced too much then it becomes necessary to stop and to clean the heat exchanger. In general terms, this can involve dismantling the heat exchanger and physically cleaning the surfaces. To maintain overall process operation one or more “spare” heat exchangers must then be provided which can be put “on-line” whilst others are being cleaned.